1. The Field of the Invention
The present invention generally relates to optical transceiver devices. More particularly, the present invention relates to structures and methods for transmitting analog control signals between transceiver components while reducing the number of connections required to do so.
2. The Related Technology
Fiber optic technology is increasingly employed as a method by which information can be reliably transmitted via a communications network. Networks employing fiber optic technology are known as optical communications networks, and are marked by high bandwidth and reliable, high-speed data transmission.
Optical communications networks employ optical transceivers in transmitting information via the network from a transmission node to a reception node. An optical transceiver at the transmission node receives an electrical signal from a host device, such as a computer, and converts the electrical signal via a laser to an optical signal. The optical signal can then be transmitted in a fiber optic cable via the optical network, such as a LAN backbone, for instance. The optical signal is then received by a remote reception node of the network. Once received by the reception node, the optical signal is fed to another optical transceiver for conversion into electrical signals. The electrical signals are then forwarded to a host device, such as a computer, for processing. The optical transceivers described above have both signal transmission and reception capabilities; thus, the transmitter portion of the transceiver converts an incoming electrical signal into an optical signal, whereas the receiver portion of the transceiver converts an incoming optical signal into an electrical signal.
The majority of components included in the optical transceiver are positioned on a printed circuit board (“PCB”). These components include a controller, which governs general operation of the transceiver, a laser driver for controlling operation of the laser in the transmitter portion, and a post-amplifier for controlling the conversion of incoming optical signals into electrical signals in the receiver portion. These components are typically incorporated into integrated circuits on the PCB.
The controller is operably connected to both the laser driver and the post-amplifier in order to govern their operation and to ensure proper transceiver function. In particular, the controller is responsible for controlling one or more parameters associated with these components during operation of the transceiver. Examples of these operational parameters include the rise time and amplitude of the electrical data signal that is conditioned by the laser driver, the rise time and amplitude of the data signal conditioned by the post-amplifier, and hysteresis and threshold set points for loss of signal detection circuitry in the post-amplifier. Each of these operational parameters is adjusted by a control device, such as a control amplifier, that is included in either the post-amplifier or the laser driver. In known systems, the controller controls the operational parameters via a plurality of analog signal lines that interconnect the controller with the respective control amplifier on the laser driver or the post-amplifier. Because of their analog nature, one analog control line extending between the controller and the respective control amplifier is typically required for each parameter over which control is desired. This creates added complexity and expense to the design and manufacture of the transceiver PCB. Additionally, this requires each IC to be larger in size.
There is therefore a need for an optical transceiver that enables control over the various operational parameters of the transceiver components while minimizing the complexity and cost of the transceiver. Moreover, it would be particularly useful to design the optical transceiver such that the integrated circuits that implement transceiver functionality are configured with a minimum of interconnects and pins, thereby reducing overall chip sizes within the transceiver.